Patent Application
20210067893
This disclosure provides a system and method for improving the response of sound systems using complementary audio output, in particular in the field of sound and audio applications.
More specifically, the present disclosure provides a sound system, the sound system comprising: a first loudspeaker, comprising at least one first speaker element, a second loudspeaker, comprising at least one second speaker element, wherein the first and second loudspeaker have at least partially overlapping frequency ranges, and the first speaker is configured to produce a response within at least one first operating band defined within the frequency range of the first speaker, and the second speaker is configured to produce a response within at least one second operating band defined within the frequency range of the second speaker, and the first and second operating bands do not overlap, and wherein the overall response of the sound system at a first location is comprised of the response within the first operating band and the response within the second operating band.
A listening room or listening space has a significant effect on an audio system's sound output at the listener position or a listening position or location. The interaction between the acoustics of a space and loudspeaker radiation is complex. Each space changes somewhat the monitor's response in a unique way, e.g. reflective vs. damped rooms, or placement against a wall vs. on a stand away from the walls. The effect of the listening space may be termed the “room response”. The effect of the listening space may therefore cause disadvantageous effects on the sound quality of the sound system, speaker system, individual loudspeaker or individual speaker element. When the effect of the listening space is minimized by calibration, this results in a system having a more consistent sound character with a flat frequency response at the listening position. In this way, the different acoustic spaces (rooms) begin to sound more systematically similar than without calibration. This results in a neutral sound character, meaning sound that doesn't decrease or increase on certain frequencies but contains an equal amount of all audible frequencies i.e. a flat frequency response.
The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
According to a first aspect of the present invention, there is provided a sound system, the sound system comprising: a first loudspeaker, comprising at least one first speaker element, a second loudspeaker, comprising at least one second speaker element, wherein the first and second loudspeaker have at least partially overlapping frequency ranges, and the first speaker is configured to produce a response within at least one first operating band defined within the frequency range of the first speaker, and the second speaker is configured to produce a response within at least one second operating band defined within the frequency range of the second speaker, and the first and second operating bands do not overlap, and wherein the overall response of the sound system at a first location is comprised of the response within the first operating band and the response within the second operating band.
According to a second aspect of the present invention, there is provided a method of improving the quality of the response of a sound system, the method comprising: measuring at a first location the room response of a first speaker to obtain a first response, measuring at the first location the room response of a second speaker to obtain a second response, analyzing the first and second responses, based at least partly on the analysis, dividing the frequency range of the first and second response into operating bands, based at least partly on the analysis, assigning the first or the second speaker to each operating band, based at least partly on the assigning, generating a first set of filters for the first speaker and a second set of filters for the second speaker, and providing the first set of filters to the first speaker and the second set of filters to the second speaker in order to implement an overall sound system response.
Various embodiments of the first or second aspect may comprise at least one feature from the following bulleted list:
In at least some of the embodiments of the disclosure, a non-transitory computer readable medium is provided having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to perform at least some of the above-mentioned aspects of the invention, optionally including the features presented in the bulleted list above.
The present disclosure provides a system and a method comprising measurement, analysis and equalization of speaker elements in order to reduce the effect of the room at the listener position. More specifically, the overall response of the sound system is measured and divided into operating bands, wherein selected responses are then assigned to each operating band in order to achieve an optimal response.
The resulting response at the listening position for a specific space is tied to both the location of the speaker and the listening position. Changing the position of the speaker with respect to a listening position, changing the listening position with respect to the speaker or changing both positions within a given room will result in a change in the resulting response at the listener location.
Within the present disclosure this effect is beneficially utilized to produce an overall flat frequency response in a given room by selectively using frequency ranges from selected loudspeakers which are less affected by the effect of the listening space in the selected frequency ranges.
The measuring process comprises determining the operating frequency range of the individual units by the analysis of individual in-room responses of individual reproduction elements at the at least one microphone locations, by assessing a number of metrics as disclosed elsewhere in this disclosure. The frequency range, also termed the operating frequency range, begins at the minimum frequency and continues to the maximum frequency emitted by the speaker element or loudspeaker or sound system. In other words, the frequency range is the range that the device is capable of expressing sound within.
Filters are designed to fit the individual unit response to the magnitude target, and all-pass filter optimisation used to match the individual unit response at the listener position. By reducing the dips in the response, the effect of the room is reduced at the listener position. Filters in accordance with the present disclosure may comprise at least one of the following: all-pass filters, roll-off filters, shelving filters, band-stop filter, band-pass filters, parametric filters, in particular a parametric shelving filter which has one or more sections which each implements a second-order filter function involving at least three arguments: the center frequency, the Q, and the gain which determines how much those frequencies are boosted or cut relative to frequencies significantly above or below the center frequency selected. It is understood that in the context of the present disclosure responses which are not being used within a specific operating band may be muted, i.e. the entirety of the response is filtered within the specific operating band. Optimisation of the all-pass equaliser parameters and group delay may be performed via any suitable methods including calculation methods disclosed herein.
Loudspeakers are used within the context of the present disclosure to produce sound, i.e. to produce an individual response, the response having a magnitude over a frequency range. Loudspeakers typically comprise a cabinet and speaker elements. Loudspeakers within the present disclosure may be active loudspeakers wherein at least one amplifier is within the loudspeaker cabinet. Benefits of an active loudspeaker are that the amplifier will match the speaker element requirements and that the digital sound processing components, DSP, can be included within the cabinet. However, so-called passive loudspeakers are also usable with the methods and devices presented herein.
A loudspeaker in accordance with the present disclosure may comprise a so-called M-way speaker, which is speaker with M individual sections. For example, a speaker may be a 2-way loudspeaker comprised of a woofer element and a tweeter element, or a speaker may be a 3-way loudspeaker comprised of a woofer element, a midrange element and a tweeter element. A loudspeaker may also be comprised of a subwoofer element, which is a speaker element. Loudspeakers may be active speakers or passive speakers. The speaker elements may be dynamic speaker elements or other types of elements usable to convert electrical signals into audio.
A sound system comprising at least one loudspeaker is used within the present disclosure to produce the total system response. For example, a sound system comprising two speaker elements X and Y, wherein first speaker element X produces response x1 and second speaker element Y produces response y1, will have a total system response of x1y1. The total system response is linked to the listener position, which is a stationary position within a space such as a room. The listener position may be determined by the features of the room, via analysis or via calibration. The sound system may also comprise a microphone, a microphone amplifier, a sound source and/or a network interface. Benefits of including a microphone are that the system will have the possibility for closed-loop control.
A loudspeaker has an anechoic response, which is the response the loudspeaker produces in the absence of any other responses, i.e. when the room response is zero. A loudspeaker is comprised of a cabinet, which may also be called an enclosure, at least one speaker element. An active loudspeaker is further comprised of an amplifier and optionally a digital sound processor, DSP. A cabinet defines the physical volume of the loudspeaker and has a major effect on the acoustic properties of the speaker. Cabinets which are at least partially comprised of aluminium are beneficial for the rigidity of construction of the cabinet, coupled with the lightness of the cabinet.
In accordance with the present disclosure, magnitude targets for responses may be set and utilized as part of at least some of the determinations used within the embodiments of the disclosure. A magnitude target may be expressed relative to another speaker or response thereof, or as an absolute dB, decibel, value. A magnitude target for a given local response, global response and/or overall response may be expressed in decibels, such as 80 dB to 100 dB, in particular 85 dB. A relative target may be 0 dB relative to response of at least one other speaker. The effect of achieving a response meeting the magnitude target is that the system then has sufficient or even ideal performance at the given frequency or for the overall response.
In a further exemplary embodiment in accordance with the present disclosure, the frequency range presented on the x-axis of
The second speaker 520 and the third speaker 530 may be identical to the first speaker 510 or they may differ in characteristics such as components used, frequency range, type of digital sound processing, et cetera. The speakers may have different locations with respect to the listening position.
In an exemplary method usable with the embodiment illustrated in
The individual responses for each of the individual elements at the microphone locations are analysed and evaluated using a number of metrics comprising at least one of the following local and global values or calculations: flatness of response, magnitude of the response, slope of the response, average magnitude of the response, weighted average of the response, notch characteristics including position and slope degree of the notch. Fourier analysis and/or Fourier methods may be used at least in part to evaluate the responses. The result of the analysis and evaluation is that individual operating bands for each unit are determined. Filters are then designed for each of the individual sections to match the response to the individual band target response, i.e. filters for each speaker are designed to achieve the required response in each band. Such filters may comprise any of the filters disclosed within this document. All-pass equalisation and group delay is optimised for the individual units to ensure maximum summing of the complex responses.
To elaborate, frequency response graphs of the output of the speakers are generated by the network device 502. After the responses have been generated, analysis of the responses performed based on the metrics to obtain an indication of flat portions, peaks and notches in the response. Obtaining the indication may also be termed a first determination and may utilize the metrics and calculation methods disclosed within this disclosure. The indication from an individual speaker is then evaluated with respect to the same indication from the other speakers. The optimal solution is then solved via calculation methods done on the measured response and/or a simulated response comprising at least the following: least squares method, linear least squares method, non-linear least squares method, ordinary least squares method, weighted least squares method, generalized least squares method, partial least squares method, total least squares method, non-negative least squares method, ridge regression method, regularized least squares method, least absolute deviations method, iteratively reweighted least squares method, bayesian linear regression, bayesian multivariate linear regression, linear regression, polynomial regression, binomial regression. Values involved in the calculations are at least one of the following variables of the measured or simulated response: flatness, magnitude, slope, average magnitude, weighted average, notch characteristics including position and slope degree of the notch. Fourier analysis and/or Fourier methods may be used at least in part in said calculations.
Based on the calculations, a total system response is generated wherein selected frequency bands are assigned to specific loudspeakers in order to achieve said generated total system response. The calculations may optionally comprise at least one of the following: magnitude optimization of the individual bands, phase optimization.
Implementation of the total system response is achieved by creating filters for the individual speakers and transmitting said filters to the speakers. The filters may be implemented by the digital signal processor, DSP, of the speaker. The speakers may store the filters within the enclosure. Said filters may be also stored on a remote server, for example to prevent data loss. Filters may be stored as a set for at least the following: for the entire system, for each band, for each speaker, for each loudspeaker element. Storing filters and filter sets as digital files allows for the possibility of backup and export of the filters, for example in cases wherein multiple rooms have identical acoustic properties and identical sound systems are installed in each room. The implementation may optionally be verified by repeating the measurement and optionally by repeating the analysis, filter generation and filter implementation steps of the method, with a beneficial effect of having increased accuracy. Such repetition may be termed an iterative process.
In a third exemplary embodiment in accordance with the present disclosure, the responses of multiple pairs of speakers are adjusted in accordance with the methods presented herein. More specifically, the response of a pair of speakers is first measured using a microphone at the listening position and then another pair of speakers, having a different room position is measured.
In a fourth exemplary embodiment in accordance with the present disclosure and illustrated in
The overall response of sound system 600 may be obtained via methods consistent with the methods presented in the disclosure, namely using a measuring microphone and measuring the response based on a test signal from 10 Hz to 21 kHz, or vice versa. At least one of the following will be measured as part of the measurement process: overall response of the sound system, individual responses from the speakers.
In a fifth exemplary embodiment in accordance with the present disclosure the sound system 700, illustrated in
In a beneficial exemplary embodiment of the invention the speaker elements are identical, meaning that they have 100% overlap of frequency range. It is also possible that a subset of the total number of speaker elements are identical, for example a three-element speaker may have two identical elements and one non-identical element. Multiple such speakers, e.g. a pair of three-way speakers is also a very suitable sound system for use in accordance with the disclosure presented herein. Overlap between the speaker elements provides flexibility in the total response when speaker elements are situated in different locations on the enclosure. Use of different types of speaker elements provide increased frequency range, especially at very high frequencies and/or very low frequencies.
An exemplary method in accordance with the present disclosure is presented in
In step 802, the measured responses are analysed. The measured responses are stored and analysis is conducted based on a number of metrics as discussed within this disclosure to determine the frequency and magnitude plot of each speaker. The analysis may be done by network interface 502, singly or jointly by any of the DSP's in the sound system such as 611 or 612, or in an alternative exemplary method, by uploading the files to a remotely located server which performs the analysis.
In step 803, the bands of operation are determined as disclosed elsewhere in this disclosure. This step may be done in conjunction with step 802 either by network interface 502 or by a remote server. In step 804, the target responses are determined via modelling of the expected target response. Step 804 may be performed individually for each speaker element or for the system as a whole, either globally or one operating band at a time. In step 805, magnitude optimization of the determined individual bands is conducted. Finally, in step 806, phase optimization is conducted for the final system response. Subsequently, the filters for the speakers are generated and transmitted to the speakers, as disclosed elsewhere within this document.
In step 901, the responses of the speakers within a sound system are measured in accordance with any suitable measuring techniques, including those disclosed within this document. The responses are stored for analysis. In step 902, the responses are analysed in accordance with the techniques disclosed within this document. In step 903, the frequency range of the sound system, which is determined either by preset or by the minimal and maximal frequency of the measured responses, is divided into operating bands in accordance with the division methods disclosed within this document. In step 904, optimal responses are determined for each band in accordance with the methods for determination as disclosed within this document. In step 905, each operating band is assigned its optimal response, i.e. the response of the one or more speakers are selected which provide the flattest response within the operating band. In step 906, the filters corresponding with the assignments are generated for each speaker individually, in accordance with the generation procedures disclosed within this document. Equalization may be done as part of the filter generation process as disclosed within this document. In step 907, the filters are provided to each speaker in accordance with the provision procedures disclosed within this document.
In accordance with the embodiments presented herein, the overall response of the sound system at a first location is comprised of the responses within the operating bands, wherein one or more responses may be selected for use within the operating band and wherein the operating bands may partially overlap. In a further exemplary embodiment, some of the loudspeakers within the sound system are used with bands and at least one speaker is used as is, i.e. the natural response of the speaker is used. This has the beneficial effect of minimizing the amount of processing required in the system.
In an exemplary embodiment, the overall response may consist of the responses within the operating bands, wherein one or more responses may be selected for use within the operating band. This has the beneficial effect of further improvement to the response flatness.
Advantages of the present disclosure include that a flatter overall response is produced at one or more listener positions. In addition, the effect of different rooms on the output of the sound system is minimised, as the conditions can be accounted for. Speakers can also be placed more flexibly within the rooms as any adverse effects on the total response can be minimised.
With respect to digital sound processing done locally or remotely, sound processing may be done using for example, at least one computing device such as at least one of the following: computing device, mobile device, server, node, cloud computing device. A computing device may be located within the speaker and comprise the DSP, or alternatively or additionally the computing device may be located within the network interface. The computing device comprises at least one processor, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. The processor may comprise more than one processor. A processing core may comprise, for example, a Cortex-A8 processing core by ARM Holdings or a Steamroller processing core produced by Advanced Micro Devices Corporation. The processor may comprise at least one Qualcomm Snapdragon and/or Intel Core processor, for example. The processor may comprise at least one application-specific integrated circuit, ASIC. The processor may comprise at least one field-programmable gate array, FPGA. The processor may be a means for performing method steps in the computing device. The processor may be configured, at least in part by computer instructions, to perform actions. In the context of the present disclosure, it is understood that the sound processing may be completed by several devices in cooperation.
Devices such as loudspeakers, microphones and network interfaces may interface with each other and external computing devices using at least one of the following technologies: direct wiring such as electrical wires, coaxial cable, fiber optic cable, infrared transmission, Bluetooth, wireless local area network, WLAN, Ethernet, universal serial bus, USB, and/or worldwide interoperability for microwave access, WiMAX, and satellite communication methods, for example. Alternatively or additionally, a proprietary communication framework may be utilized. In some embodiments, separate networks may be used for one or more of the following purposes: communication between loudspeakers, communication between loudspeakers and network interfaces, communication between network interfaces and servers, et cetera.
It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In this description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, that is, a singular form, throughout this document does not exclude a plurality.
At least some embodiments of the present invention find industrial application in audio engineering, more specifically in providing optimized or improved responses for sound systems.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20195726 | Sep 2019 | FI | national |
